Use UserHandle#getIdentifier to get the userid

UidRange uses PER_USER_RANGE to calculate and get the userid,
but PER_USER_RANGE is a hidden API, so use getIdentifier to get
the userid instead.

Bug: 170598012
Test: atest FrameworksNetTests:UidRangeTest
Change-Id: I06ab0f2da8a33d2b718bbc3a609d3d6a5fe0a095
diff --git a/core/java/android/net/UidRange.java b/core/java/android/net/UidRange.java
index f0e7da7..be5964d 100644
--- a/core/java/android/net/UidRange.java
+++ b/core/java/android/net/UidRange.java
@@ -52,12 +52,12 @@
 
     /** Returns the smallest user Id which is contained in this UidRange */
     public int getStartUser() {
-        return start / PER_USER_RANGE;
+        return UserHandle.getUserHandleForUid(start).getIdentifier();
     }
 
     /** Returns the largest user Id which is contained in this UidRange */
     public int getEndUser() {
-        return stop / PER_USER_RANGE;
+        return UserHandle.getUserHandleForUid(stop).getIdentifier();
     }
 
     public boolean contains(int uid) {